356  Rhus  Venenata,  or  Poison  Sumach.  {AMAugUT 
Am.  Jour.  Phai  m. 
1874. 
It  was  at  first  supposed  that  this  acid  was  the  same  which  Gmelin 
speaks  of  in  his  Hand-Book  (this  being  the  only  work  where  anything 
was  found  in  any  way  touching  upon  this  plant  or  genus)  under  the 
name  of  rhus-  tannic  acid,  and  said  to  be  a  constituent  of  the  plants 
of  this  genus.  But  it  is  found  that  this  acid  has  none  of  the  proper- 
ties characteristic  of  the  astringent  acids  ;  it  has  not  an  astringent 
taste  ;  does  not  precipitate  gelatin  nor  iron.  Owing  to  the  small 
quantity  of  the  leaves  originally  taken,  and  the  small  amount  of  time 
that  could  be  devoted  to  the  work,  the  examination  could  not  be  fur- 
ther continued. 
If  so  desired,  this  acid  can  be  obtained  in  any  quantity  by  boiling 
the  dry  powdered  leaves  with  water  for  some  time,  straining,  express- 
ing and  filtering  while  hot  ;  then  boiling  with  and  filtering  through 
animal  charcoal,  precipitating  with  neutral  acetate  of  lead,  decom- 
posing the  precipitate  with  sulphuretted  hydrogen  gas,  filtering  out 
the  sulphide  of  lead,  then  evaporating  and  crystallizing.  The  crys- 
tals can  be  purified  by  re-crystallization  from  water  solution,  if  so 
desired.  It  is  found  by  experiment  that,  in  passing  the  decoction 
through  animal  charcoal,  the  charcoal  retains  all  of  the  coloring 
matter  with  nearly  all  of  the  gum,  but  not  taking  up  any  recognizable 
quantity  of  the  acid. 
Other  crystals  were  obtained  from  portion  third  cf  the  decoction, 
rafter  having  filtered  out  the  precipitate  caused  by  alum  and  ammonia, 
by  evaporating  the  filtrate  and  allowing  it  to  crystallize.  These 
crystals  are  deposited  needle-shaped,  and  as  long  triangular  prisms. 
In  shape,  they  resemble  the  first-mentioned  crystals  of  this  acid,  but 
are  very  much  larger.  They  have  a  sharp,  salty  taste,  and  are  neu- 
tral in  reaction  ;  are  soluble  in  water,  hydrochloric,  nitric,  sulphuric 
and  acetic  acids  ;  very  soluble  in  ether,  insoluble  in  alcohol,  unless 
added  in  very  large  quantities.  The  crystals  suffer  decomposition 
instead  of  sublimation,  and  when  completely  burned  leave  a  small 
white  ash.  The  possibility  of  this  being  a  compound  formed  from 
any  of  the  reagents  added,  or  by  their  decomposition,  was  satisfac- 
torily precluded  by  special  examination  for  that  purpose.  It  is  sup- 
posed that  this  is  an  alkaline  earth  in  combination  with  an  organic 
acid,  probably  the  same  acid  which  was  previously  obtained  separate, 
though  the  reactions  of  these  two  sets  of  crystals  differ  in  a  few  in- 
stances. 
University  of  MicMgan,  July  3,  1874. 
